Openwhyd - Collect and Share the tracks you love.
Spotify - Map shows when two people play same song at same time
Music Smasher - Find any song. Music Smasher searches Spotify, Rdio, SoundCloud, Bandcamp, and YouTube.
SoundCloud - Enjoy music & follow favourite artists
FoxTube - Play YouTube video continuously with playlists. FoxTube features:
Ampache - Web ( HTTP centralized ) based audio/video streaming application